Support member for a superconducting magnet assembly

ABSTRACT

A superconducting magnet assembly is described wherein the magnet cartridge is suspended within the vacuum chamber by a single support member extending from a wall of the vacuum chamber to the magnet cartridge. In one aspect, the support member includes a support tube and a joint attached to an end of the support tube. The joint is attached to the wall of the outer vacuum chamber, and provides at least one degree of freedom to the support tube relative to the wall. In another aspect, a joint is attached to an opposite end of the support tube, and is attached to the magnet cartridge for providing at least one degree of freedom to the support tube relative to the magnet cartridge. In another aspect, the support is constructed from one or more sections and the material choice is governed by the requirements for strength, stiffness, and thermal conductivity.

CROSS REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of a priority under 35 U.S.C.119 to Great Britain Patent Application No. 0228780.3 filed Dec. 10,2002, the entire contents of which are hereby incorporated by reference.

BACKGROUND OF INVENTION

[0002] This invention relates to support members for super-conductingmagnet assemblies. More particularly, the invention relates to a supportmember for suspending a magnet cartridge within a vacuum chamber in asuperconductor magnet assembly.

[0003] Superconducting magnets typically include a magnet cartridgesuspended within an outer vacuum chamber by a plurality of supportmembers, which extend from the outer vacuum chamber to the magnetcartridge. Disposed between the magnet cartridge and the outer vacuumchamber is a radiation shield, through which the support members extend.

[0004] To facilitate the superconductivity of the electrical wiringwithin the magnet cartridge, the magnet cartridge is maintained at atemperature that approaches absolute zero. However, the walls of theouter vacuum chamber are subject to ambient (room) temperature. Tomaintain this large temperature gradient, the magnet assembly isdesigned to reduce convection, radiation, and conduction heat transferbetween the magnet cartridge and the walls of the outer vacuum chamber.

[0005] A reduction in convection heat transfer is accomplished bymaintaining a vacuum within the outer vacuum chamber. A reduction inradiation heat transfer is accomplished by the radiation shield, and areduction of conductive heat transfer is accomplished through the designof the support members.

[0006] The support members are subjected to the large temperaturegradient—with the end of the support member at the magnet cartridgesubjected to temperatures approaching absolute zero, and the end of thesupport member at the outer vacuum chamber subjected to roomtemperature. The support members are designed to have very low thermalconductivity and to cater for the effects of differences in thecoefficient of thermal expansion of the different materials used in theconstruction of the magnet and the suspension system. In addition to thethermal stresses, the support members must be designed to withstandforces applied by the magnet. These forces include the weight mass ofthe magnet, which can be many tons, and the forces induced by themagnet, which can be even greater. The support members must havesufficient stiffness to prevent motion of the magnet when these forcesare applied.

[0007] Typically, the support members are long, thin rods. Because therods are long and thin, the heat transfer area is small, which is anadvantage in preventing conductive heat transfer. However, these rodsprovide support in tension only and would buckle if exposed to acompressive load while the forces applied to the support members by themagnet are not constant in direction. Thus, to ensure that the magnetcartridge is supported under the varying forces, the rods are arrangedin a matrix surrounding the magnet cartridge.

[0008] While such support members are effective in supporting the magnetcartridge, the use of such support members has drawbacks. First, as thenumber of rods used in the array increases, the conductive heat transferarea also increases. In addition, the number of penetrations through theradiation shield also increases, which decreases the effectiveness ofthe radiation shield, and increases the labor necessary to seal each ofthe penetrations from radiation leakage. Second, the rods must beaccurately positioned (e.g., in diametrically opposed fashion) and aretypically pre-tensioned. The accurate positioning of the rods and thepre-tensioning of the rods add to the cost of manufacturing the magnetassembly.

SUMMARY OF INVENTION

[0009] The above-described drawbacks and deficiencies are overcome oralleviated by a superconducting magnet assembly wherein the magnetcartridge is suspended within the vacuum chamber by a single supportmember extending from a wall of the vacuum chamber to the magnetcartridge. In one aspect, the support member includes a support tube anda joint attached to an end of the support tube. The joint is attached tothe wall of the outer vacuum chamber, and provides at least one degreeof freedom to the support tube relative to the wall. In another aspect,a joint is attached to an opposite end of the support tube, and isattached to the magnet cartridge for providing at least one degree offreedom to the support tube relative to the magnet cartridge. In anotheraspect, the support is constructed from one or more sections and thematerial choice is governed by the requirements for strength, stiffness,and thermal conductivity.

[0010] The above discussed and other features and advantages of thepresent invention will be appreciated and understood by those skilled inthe art from the following detailed description and drawings.

BRIEF DESCRIPTION OF DRAWINGS

[0011] Referring to the exemplary drawings wherein like elements arenumbered alike in the several Figures:

[0012]FIG. 1 is a schematic diagram of a superconducting magnetassembly;

[0013]FIG. 2 is an isometric view of a support member for thesuperconducting magnet assembly of FIG. 1;

[0014]FIG. 3 is a cross-sectional view of the support member of FIG. 2;

[0015]FIG. 4 is an isometric view of an end joint on the outer vacuumchamber side of the support member of FIG. 2; and

[0016]FIG. 5 is an isometric view of an end joint on the magnetcartridge side of the support member of FIG. 2.

DETAILED DESCRIPTION

[0017] Referring to FIG. 1, a superconducting magnet assembly 10 isshown. Superconducting magnet assembly includes a magnet cartridge 12suspended within an outer vacuum chamber 14 by a single support member16. Disposed between magnet cartridge 12 and a wall 18 of outer vacuumchamber 14 is a radiation shield 20, through which support member 16extends. A thermal coupling 22 extends between support member 16 andradiation shield 20. Support member 16 is fixedly secured to wall 18 andmagnet cartridge 12 such that support member 16 transmits axiallycompressive and tensile loads from magnet cartridge 12 to wall 18.

[0018] During operation, magnet cartridge 12 is maintained at a lowtemperature (e.g., near absolute zero), while the wall 18 of outervacuum chamber is subject to the temperature of the room in whichsuperconducting magnet assembly 10 is placed. Thus, during operation atemperature differential exists along support member 16.

[0019] Referring to FIG. 2, an isometric view of support member 16 isshown. Support member 16 has an outer vacuum chamber end 50 and a magnetcartridge end 52. Disposed on ends 50 and 52 are joints 54 and 56 andtube couplings 58 and 60. Extending between tube couplings 58 and 60 isa support tube 62. Attached to a central portion of support tube 62 isthermal coupling 22.

[0020] When support member 16 is installed, ends 50 and 52 are securedagainst wall 18 and magnet cartridge 12, respectively. Tensile andcompressive forces are transmitted from magnet cartridge 12, throughjoint 56 and tube coupling 58 to support tube 62, and from support tube62 through tube coupling 56 and joint 54 to wall 18. As will bediscussed in further detail hereinafter, each of joints 54 and 56 arevery stiff axially, but allow support tube 62 to pivot through smallangles. The joints 54 and 56 compensate for manufacturing tolerances,build errors, and the effect of differential thermal expansion, andtranslate pure axial tension and compression forces on the support tube62.

[0021] Referring to FIG. 3, a cross-sectional view of support member 16is shown. End 50 of support member is secured against wall 18 by aflange 100, which captures a circumferential ridge 102 formed on joint54. Flange 100 is secured to wall 18 by welding, bolting, or the like.Joint 54 is secured to tube coupling 58 by a plurality of bolts 103,which are recessed in joint 54 by way of through holes 104 in joint 54.Bolts 103 engage a collar 106, which is disposed around the periphery ofsupport tube 62. While an exemplary embodiment is described herein, itwill be appreciated that end 50 and 52 may be secured against wall 18and magnet cartridge 12, respectively, using any suitable means.

[0022] In the embodiment shown, support tube 62 is an elongated cylinderof generally uniform thickness having regions of increased thickness. Afirst region of increased thickness 108 is formed near end 50, where theoutside diameter of support tube 62 is increased abruptly such that adiametrical ridge 110 is formed. From the ridge 110 to the end of thetube 62, the outside diameter is increased gradually to create taper. Asecond region of increased thickness 112 is formed near the center ofsupport tube 62, where the outside diameter of the support tube isincreased. The second region of increased thickness 112 provides supportfor the thermal coupling 22. The third region of increased thickness 114is formed near end 52, where the inside diameter is decreased abruptlysuch that a diametrical ridge 116 is formed. From the ridge 116 to theend of the tube 62, the inside diameter is decreased gradually to createtaper.

[0023] Support tube 62 may be constructed of any thermally insulativematerial such as, for example, fiberglass, carbon (graphite) fiber,plastic, or the like. Support tube 62 may also be a composite structure,including more than one material. Where a support tube 62 is a compositestructure, the materials are selected based on the performance of thematerial at the temperatures applied to the different portions of thesupport tube 62. For example, the portion of support tube 62 extendingfrom the second region of increased thickness 112 toward end 50 may beconstructed of a fiberglass material, which has good strength propertiesat temperatures around room temperature, and the portion of support tube62 extending from the second region of increased thickness 112 towardthe end 52 may be constructed of a carbon fiber material, which has goodstrength properties at temperatures approaching absolute zero.

[0024] Disposed within the support tube 62 at the first region ofincreased thickness 108 is a cylindrical plug 118. Cylindrical plug 118and collar 106 form the tube coupling 58, which secures the support tube62 to the joint 54. An inside diameter of collar 106 is tapered to matchthe taper at the first region of increased thickness 108. The taper ofthe collar acts to provide a compressive force onto the first region ofincreased thickness 108 as the collar 106 is drawn towards the joint 54by the tightening of screws 103. The plug 118 acts to support the insideof the support tube 62 against the compressive force of the collar 106.The inside diameter of the collar 106 includes a ridge, which interactswith the diametrical ridge 110 on the support tube 62. Together, thecollar 106 and plug 118 secure the end of the support tube 62 againstthe joint 54 when the support tube 62 is under an axially tensile load.Plug 118 and collar 106 may be manufactured from a rigid material suchas, for example, stainless steel or titanium.

[0025] Disposed within support tube 62 is a thermal baffle assembly 120.The thermal baffle assembly 120 includes a support rod 122 that issecured at one end to plug 118, and extends along the longitudinal axisof the tube 62. Secured to support rod 122 is a series of spaced-apartdisks 124. The disks 124 act as baffles to intercept heat radiationthrough the tube 62. The disks 124 and support rod 122 may beconstructed of a thermally insulative material such as, for example,plastic, fiberglass, aluminized Mylar or carbon fiber.

[0026] Attached to the support tube 62 at the second region of increasedthickness 112 is the thermal coupling 22. A cylindrical portion ofthermal coupling 130 is disposed around support tube 62 and attachedthereto by fasteners, adhesive, or the like. Extending from cylindricalportion 130 towards end 50 is a conical portion 132. A plurality ofthermally conductive braids 134 extend from an end of conical portion132 towards end 50, and a second cylindrical portion 136 is, in turn,coupled to the ends of the braids 134. Extending radially from an end ofsecond cylindrical portion 136 distal from the braids 134 is a flange138. Flange 138 is coupled to the radiation shield 20 using, forexample, fasteners, adhesive, welding, or the like. Thermal coupling 22may be constructed of a thermally conductive material, such as copper.

[0027] Thermal coupling 22 acts to shunt the conduction of heat from theouter vacuum chamber wall 18 to the radiation shield 20, and therebyprevent the conduction of heat to the magnet cartridge 12 via thesupport member 16. Braids 134 prevent vibration of the radiation shield20 from traveling to the magnet cartridge 12 via the support member 16,and also prevent the forces applied to the support member 16 from beingtransmitted to the radiation shield 20.

[0028] The third region of increased thickness 114 on the support tube62 is captured by the tube coupling 60. Tube coupling 60 comprises abolt 140, a washer 142, a plug 144, and a sleeve 146. The bolt 140extends along the longitudinal axis of the support member 16, throughthe washer 142, plug 144, and joint 56, and threadably engages an endcap 148. An outside diameter of the plug 144 is tapered to match thetaper at the third region of increased thickness 144. The taper of theplug 144 acts to provide a compressive force onto the inside diameter ofthe third region of increased thickness 114 as the plug 144 is drawntowards the joint 56 by the tightening of bolt 140. The collar 146 actsto support the outside of the support tube 62 against the compressiveforce of the plug 144. The outside diameter of the plug 144 includes aridge 148, which interacts with the diametrical ridge on the insidediameter of the support tube 62. Together, the collar 146 and plug 144secure the end of the support tube 62 against the joint 56 when thesupport tube 62 is under an axially tensile load. Plug 144, bolt 140,washer 142, and collar 146 may be manufactured from a rigid,non-magnetic material such as, for example, titanium.

[0029] End cap 148 is secured to the magnet cartridge 12 by way offastener, welding, adhesive, or the like. Joint 56 is captured betweentube coupling 60 and end cap 148 when bolt 140, which is threaded intoend cap 148, is tightened.

[0030] Referring now to FIGS. 4 and 5, the construction of joints 54 and56 will be described. Each joint 54 and 56 includes first, second, andthird disks 200, 202 and 204. The first disk 200 is coupled to thesecond disk 202 by a beam 208, which extends along a diameter of thefirst disk 200. The first disk 200 includes wedges 210 extendingtherefrom along either side of the beam 208. The wedges 210 are receivedwithin recesses 212 formed in the second disk 202. Similarly, the seconddisk 202 is coupled to the third disk 204 by a beam 214, which extendsalong the diameter of the second disk 202. The second disk 202 includeswedges 216 extending therefrom along either side of the beam 214. Thewedges 216 are received within recesses 218 formed in the third disk204. In the embodiment shown, each joint 54 and 56 is machined from asolid cylinder of rigid, non-magnetic metal, such as titanium orInconnel. Two diametrically opposed slots 220 and 222 disposed in thecylinder form the space between each disk 200 and 202, each beam 208,two wedges 210, and two recesses 212.

[0031] Similarly, two diametrically opposed slots 224 and 226 disposedin the cylinder form the space between each disk 202 and 204, each beam214, two wedges 216, and two recesses 218.

[0032] The bending of beams 208 and 214 provides two degrees of freedomto each joint 54 and 56. Thus, while each joint 54 and 56 is very stiffaxially, they allow support tube 62 to pivot through small angles aboutthe y and z axes indicated in FIG. 4 and FIG. 5. The y and z axes may besituated at 90 degrees to each other and at 90 degrees to the centroidalaxis x of the support member 16. The joints 54 and 56 compensate formanufacturing tolerances, build errors and the effect of differentialthermal expansion and translate the forces applied by magnet cartridge12 into pure axial tension and compression forces on the support tube62. The wedges 210 and 216 provide lateral support to beams 208 and 214thereby preventing the buckling of beams 208 and 214. In addition, thewedges 210 and 216 help to stiffen the disk between the two beams.

[0033] The single support member 16 takes all loads in tension andcompression that a typical design would handle with a combination oftension straps. Thus, the support member 16 reduces the number of rodstypically used in supporting the magnet cartridge 12, and, therebyreduces the conductive heat transfer area from that previously possible.In addition, the number of penetrations through the radiation shield 20also decreases from designs that use a combination of tension straps.This, in turn, increases the effectiveness of the radiation shield 20and requires less labor to seal penetrations in the radiation shield 20from that previously possible. The high stiffness joints 54 and 56 takeup build errors and the effect of differential thermal expansion andtranslate them into pure axial tension and compression forces on thesupport tube 62.

[0034] While the invention has been described with reference to apreferred embodiment, it will be understood by those skilled in the artthat various changes may be made and equivalents may be substituted forelements thereof without departing from the scope of the invention. Inaddition, many modifications may be made to adapt a particular situationor material to the teachings of the invention without departing from theessential scope thereof. Therefore, it is intended that the inventionnot be limited to the particular embodiment disclosed as the best modecontemplated for carrying out this invention, but that the inventionwill include all embodiments falling within the scope of the appendedclaims. Moreover, the use of the terms first, second, etc. do not denoteany order or importance, but rather the terms first, second, etc. areused to distinguish one element from another.

What is claimed is:
 1. A superconducting magnet assembly comprising: avacuum chamber having a wall; a magnet cartridge; and a single supportmember extending from a wall of said vacuum chamber to said magnetcartridge, said single support member suspending said magnet cartridgewithin said vacuum chamber.
 2. The superconducting magnet assembly ofclaim 1, wherein said single support member includes: a support tube;and a joint attached to an end of said support tube, said joint beingattached to said wall of said outer vacuum chamber, said joint providingat least one degree of freedom to said support tube relative to saidwall.
 3. The superconducting magnet assembly of claim 2, wherein saidjoint includes first, second, and third disks, said first disk iscoupled to said second disk by a first beam extending along at least aportion of a diameter of said first disk, and said second disk iscoupled to said third disk by a beam extending along at least a portionof a diameter of said second disk.
 4. The superconducting magnetassembly of claim 3, wherein said first disk includes first wedgesextending therefrom along either side of said first beam, said firstwedges are received within first recesses formed in said second disk,and said second disk includes second wedges extending therefrom alongeither side of said second beam, said second wedges are received withinsecond recesses formed in said second disk.
 5. The superconductingmagnet assembly of claim 4, wherein said joint is machined from a solidcylinder of material.
 6. The superconducting magnet assembly of claim 1,wherein said single support member includes: a support tube; and a jointattached to an end of said support tube, said joint being attached tosaid magnet cartridge, said joint providing at least one degree offreedom to said support tube relative to said magnet cartridge.
 7. Thesuperconducting magnet assembly of claim 6, wherein said joint includesfirst, second, and third disks, said first disk is coupled to saidsecond disk by a first beam extending along at least a portion of adiameter of said first disk, and said second disk is coupled to saidthird disk by a beam extending along at least a portion of a diameter ofsaid second disk.
 8. The superconducting magnet assembly of claim 7,wherein said first disk includes first wedges extending therefrom alongeither side of said first beam, said first wedges are received withinfirst recesses formed in said second disk, and said second disk includessecond wedges extending therefrom along either side of said second beam,said second wedges are received within second recesses formed in saidsecond disk.
 9. The superconducting magnet assembly of claim 8, whereinsaid joint is machined from a solid cylinder of material.
 10. Thesuperconducting magnet assembly of claim 1, wherein said single supportmember includes: a support tube; and a baffle disposed within saidsupport tube.
 11. A support member for suspending a magnet cartridgewithin an outer vacuum chamber in a superconducting magnet assembly,said support member comprising: a support tube; and a joint attached toan end of said support tube, said joint being attached to said wall ofsaid outer vacuum chamber, said joint providing at least one degree offreedom to said support tube relative to said wall.
 12. Thesuperconducting magnet assembly of claim 11, wherein said joint includesfirst, second, and third disks, said first disk is coupled to saidsecond disk by a first beam extending along at least a portion of adiameter of said first disk, and said second disk is coupled to saidthird disk by a beam extending along at least a portion of a diameter ofsaid second disk.
 13. The superconducting magnet assembly of claim 11,wherein said first disk includes first wedges extending therefrom alongeither side of said first beam, said first wedges are received withinfirst recesses formed in said second disk, and said second disk includessecond wedges extending therefrom along either side of said second beam,said second wedges are received within second recesses formed in saidsecond disk.
 14. The superconducting magnet assembly of claim 13,wherein said joint is machined from a solid cylinder of material. 15.The superconducting magnet assembly of claim 11, wherein said singlesupport member includes: a support tube; and a joint attached to an endof said support tube, said joint being attached to said magnetcartridge, said joint providing at least one degree of freedom to saidsupport tube relative to said magnet cartridge.
 16. The superconductingmagnet assembly of claim 15, wherein said joint includes first, second,and third disks, said first disk is coupled to said second disk by afirst beam extending along at least a portion of a diameter of saidfirst disk, and said second disk is coupled to said third disk by a beamextending along at least a portion of a diameter of said second disk.17. The superconducting magnet assembly of claim 16, wherein said firstdisk includes first wedges extending therefrom along either side of saidfirst beam, said first wedges are received within first recesses formedin said second disk, and said second disk includes second wedgesextending therefrom along either side of said second beam, said secondwedges are received within second recesses formed in said second disk.18. The superconducting magnet assembly of claim 17, wherein said jointis machined from a solid cylinder of material.
 19. The superconductingmagnet assembly of claim 11, wherein said single support memberincludes: a support tube; and a baffle disposed within said supporttube.
 20. A superconducting magnet assembly comprising: a vacuum chamberhaving a wall; a magnet cartridge; and a single support member extendingfrom said wall of said vacuum chamber to said magnet cartridge, saidsingle support member suspending said magnet cartridge within saidvacuum chamber, said single support member includes: a support tube, afirst joint attached to an end of said support tube, said first jointbeing attached to a wall of said outer vacuum chamber, said first jointproviding at least one degree of freedom to said support tube relativeto said wall, and a second joint attached to an opposite end of saidsupport tube, said second joint being attached to said magnet cartridge,said second joint providing at least one degree of freedom to saidsupport tube relative to said magnet cartridge.
 21. A superconductingmagnet assembly comprising: a vacuum chamber having a wall; a magnetcartridge; and a single support member extending from a wall of saidvacuum chamber to said magnet cartridge, said single support membersuspending said magnet cartridge within said vacuum chamber, said singlesupport member includes: a support tube, a first means for providing atleast one degree of freedom to said support tube relative to said wall,and a second means for providing at least one degree of freedom to saidsupport tube relative to said magnet cartridge.
 22. The superconductingmagnet assembly of claim 21, wherein said first means is coupled to saidsupport tube by a first tube coupling means, and said second means iscoupled to said support tube by a second tube coupling means.
 23. Thesuperconducting magnet assembly of claim 22, wherein said first andsecond tube coupling means each include a plug disposed within saidsupport tube and a collar disposed around a periphery of said supporttube.
 24. The superconducting magnet assembly of claim 21, wherein saidfirst and second means each includes first, second, and third disks,said first disk is coupled to said second disk by a first beam extendingalong at least a portion of a diameter of said first disk, and saidsecond disk is coupled to said third disk by a beam extending along atleast a portion of a diameter of said second disk.
 25. A method ofsuspending a magnet cartridge within an outer vacuum chamber in asuperconducting magnet assembly, the method comprising: securing thesuperconducting magnet assembly to a single support member, said singlesupport member including at least one joint disposed on a support rod.